Method of fabricating twisted-wire hybrid couplers



Sept. 1,1970 H. R. BEURRIER METHOD OF FABRICATING TWISTED-WIRE HYBRID COUPLERS Filed Feb. 2, 1968 FIG. .3

INVENTOR HR. BE URR/E'R A r TORNEV United States Patent Ofice Patented Sept. 1, 1970 ABSTRACT OF THE DISCLOSURE The electrical properties of a twisted-wire hybrid coupler depend upon the wire size and the thickness of the insulation. The method of construction disclosed utilizes bare wire and a separate sheet of insulation which wraps itself about the bare wires duringa twisting operation. v

The use of a separate insulator greatly decreases the variety of insulated wire sizes that must be stocked and increases the reproducibility of couplers since the insulator thickness can be maintained more uniform.

This invention relates to a method of manufacturing twisted-wire, lumped-impedance quadrature hybrid couplers.

BACKGROUND OF THE INVENTION Lumped-impedance quadrature hybrid couplers comprise a pair of twisted wires whose capacitance and series inductance are tailored to produce a particular characteristic impedance, and a particular powerdivision. While such couplers are small, highly eflicient and inexpensive, there are a number of practical problems associated with them which may adversely affect their cost and perfomance. For example, since the capacitance of the twistedwire pair is a function of the thickness of the dielectric material separating the two wires, variations in the thickness of the insulation on either wire causecorresponding changes in the electrical characteristics of the coupler. In the course of manufacture, such unit-to-unit variations reduce the yield and, correspondingly, increase the cost of each coupler. A second problem relates to the cost of stocking each Wire size in a variety of insulation thicknesses. Clearly, anything that would reduce'the need for such a large wire inventory would reduce the cost of manufacturing twisted-wire couplers.

SUMMARY OF THE INVENTION In accordance with the present invention, the abovedescribed problems are eliminated by a methor of con structing twisted-wire couplers which utilizes bare wire and a separate insulator. The method comprises the steps of clamping two bare wires together at both ends and pulling them taut; placing a sheet of flexible insulation between the two wires; and rotating an end of said wires about an axis parallel to the wire. This has the effect of twisting the wires about each other and, simultaneously, causing the insulation to wrap itself about the wires.

The resulting coupler is, in all respects, the same as a coupler constructed using insulated ,wire with several notable advantages. Since thin insulation sheets of uniform thickness can be readily obtained commercially, couplers constructed in accordance with the invention have more uniform characteristics than those constructed of commercially available insulated wire. Secondly, by using separate insulators, it is no longer necessary to stock each wire size in a variety of different insulator thicknesses. In addition, since both wires are bare, it is no longer necessary to strip insulation oil the wires in order to make contact to the coupler.

These and other objects and advantages, the nature of the present invention, and its various features, will appear more fully upon consideration of the various illustrat-ive embodiments now to be described in detail in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the two bare wires and the insulator in place at the beginning of the process;

FIG. 2 shows the two wires and the insulator at an intermediate stage in the process;

FIG. 3 shows the twisted-wire pair at the end of the process;

FIG. 4 is a cross-section of the twisted-wire pair.

DETAILED DESCRIPTION Referring to the drawings, FIG. 1 shows a pair of bare wires 10 and 11 clamped together at both ends anda sheet of flexible insulation 12, of desired material and thickness, placed between them. In this particular embodiment, one end of each wire is shown held in the jaws 13 of a vise, while the other end of each wire is held by the chuck 14 of a twisting mechanism.

So held, the wires are pulled taut and the twisting mechanism activated. The effect is to twist the wires about each other as indicated in FIG. 2, which shows the wires 10 and 11 and the insulator 12 at some intermediate stage in the process. It will be noted that as the wires twist about each other, the insulator 12 is also caused to twist about the wires at the same time.

As the twistingprocess continues, the insulation is observed to curl back and cover the wires, resulting in a fully insulated, compactly wound pair of wires. The twisted-wire pair at the end of the process is illustrated in FIG. 3, which shows wires 10 and 11 fully entwined with each other and with insulator 12.

FIG. 4 shows a cross-section of the final twisted-wire pair showing wires 10 and 11, and insulator 12. It will be noted that in order to fully envelope the two wires, the width of insulator sheet 12 must be at least equal to the combined circumferences of the two wires.

In practice, long lengths of wire are wound and the resulting twisted-wire pair cut to the desired lengths to form the individual hybrid couplers. As an example, a 50 ohm hybrid coupler, having a center frequency of 62 megahertz, was constructed of No. 14 Wire and a 5 mil thick sheet of Mylar insulation. The coupler was approximately 8% inches long and about 3 /2 turns per inch.

In all cases it is understood that the above-described arrangement is illustrative of but one of the many possible specific embodiments which can represent applications of the principles of the invention. For example, instead of clamping one end of the two wires in a vise, both ends can be mounted in rotatable devices which are then rotated simultaneously in opposite directions. Thus, numerous and varied other arrangements can readily be devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention.

I claim:

1. A method of fabricating a twisted-wire pair using two bare Wires comprising the steps of:

clamping the two bare wires together at both ends and pulling them taut; placing a sheet of flexible insulation between the two wires; and

rotating one end of said wires about an axis parallel to said wires thereby twisting said wires about each other and simultaneously causing said insulation to wrap itself about said wires.

3 4 2. The method according to claim 1 including the step FOREIGN PATENTS of cutting said twisted wires to size to form a hybrid 139,930 7/1930 Germany coupler of prescribed characteristics.

812.192 4/ 1959 Great Britain.

References Cited 5 JOHN F. CAMPBELL, Primary Examiner UNITED STATES PATENTS C. E. HALL, Assistant Examiner 2,558,566 6/1951 Jorgensen 336-206 X U.S. C1. X.R. 2,947,652 8/1960 Burr 57-12 10 336-206, 209; 29-505; 57-12, 156, 167; 140-449; 3,254,923 6/1966 Marks 61 al 140-49X 174 34,117.1;333-10 

